FloTrac® monitoring system: what are its uses in critically ill medical patients?

The FloTrac®/Vigileo device uses arterial pressure waveform analysis to calculate stroke volume and cardiac output; it does not require calibration against an independent measurement of cardiac output. Consequently, it provides a method to determine hemodynamic status, changes in the clinical course and responses to therapeutic interventions in patients who have arterial catheters in place. These devices perform relatively well in stable patients undergoing surgery and having an acceptable percentage error in differences between the FloTrac® device and invasive monitoring using pulmonary catheters. However, in patients with septic shock and other clinical states associated with low systemic vascular resistances, such as cirrhosis, the FloTrac® does not provided acceptable correlation with independent measurements with pulmonary artery catheters. FloTrac® measurements often underestimate the cardiac output and have unacceptably high percent error, which ranges from 30% to 60%. There is a moderate correlation with changes in cardiac output after fluid administration, but a poor correlation with changes in cardiac output after increases or decreases in norepinephrine administration. The bias between measurements increases as the systemic vascular resistance decreases. Consequently, cardiac output measurements using the FloTrac® device are not accurate enough for use in patients with septic shock, advanced liver disease and other medical conditions associated with decreased vascular tone.